The miniaturization of electronic products is one of the primary tenets of technologic advance. Competitive advantage and the success of a product line largely hinges on the ability of a company to successfully provide products that are both increasingly functional and increasingly portable. As technology advances, it becomes increasingly possible to miniaturize electronic circuitry below human scale, with the result being that the interface alone (e.g., screens, keypads, cursor control devices) come to define the size of portable products. Therefore, the ergonomic quality and size of input devices (such as keypads) continue to have a growing significance to product acceptance and success.
One type of keypad or keyboard that provides a particularly space-efficient input means are Independent And Combination Key (IACK) keypads, having arrays of effectively lower, concave combination key regions interspersed among an array of effectively elevated, convex independent key regions. IACK keypads have both independent and combination key regions, typically arranged in alternating rows and columns. Independent key regions of my prior IACK keypads were elements of the keypad that, when pressed independent of adjacent keys, produced an associated output. By contrast, the combination key regions of my prior IACK keypads were keypad elements with adjacent independent keys (such as at diagonally-oriented corners of the combination key region) with no corresponding key switches underlying the keymat. Output corresponding to the combination key region was produced by pressing two or more adjacent elevated key regions in combination.
Other improvements leading to reliable operation of increasingly miniaturized keypads are desired, even in keypads that don't require the output of some key regions to be produced by activating combinations of switches corresponding to other key regions. For example, improvements are sought in the construction of key switches that can reliably and near-simultaneously close multiple electrical connections with a single, defined tactile feedback event. There is a class of keyboards and keypads, including IACK keypads, that require multiple key switch contacts to be made simultaneously. Snap domes (made from materials such as metal and plastic) that operate in a buckling mode provide a high quality of tactile feedback. It is extremely difficult, however, to make reliable momentary connection to more than one key switch contact at a time.